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• Revision 9349a28e80 : Enable mode search threshold update in non-RD coding mode Adaptively adjust the

  28 octobre 2014, par Jingning Han

  Changed Paths :
   Modify /vp9/encoder/vp9_pickmode.c

  
   Modify /vp9/encoder/vp9_rd.c

  
   Modify /vp9/encoder/vp9_rd.h

  
   Modify /vp9/encoder/vp9_rdopt.c

  
   Modify /vp9/encoder/vp9_speed_features.c

  
  
  Enable mode search threshold update in non-RD coding mode

  Adaptively adjust the mode thresholds after each mode search round
  to skip checking less likely selected modes. Local tests indicate
  5% - 10% speed-up in speed -5 and -6. Average coding performance
  loss is -1.055%.

  speed -5
  vidyo1 720p 1000 kbps
  16533 b/f, 40.851 dB, 12607 ms -> 16556 b/f, 40.796 dB, 11831 ms

  nik 720p 1000 kbps
  33229 b/f, 39.127 dB, 11468 ms -> 33235 b/f, 39.131 dB, 10919 ms

  speed -6
  vidyo1 720p 1000 kbps
  16549 b/f, 40.268 dB, 10138 ms -> 16538 b/f, 40.212 dB, 8456 ms

  nik 720p 1000 kbps
  33271 b/f, 38.433 dB, 7886 ms -> 33279 b/f, 38.416 dB, 7843 ms

  Change-Id : I2c2963f1ce4ed9c1cf233b5b2c880b682e1c1e8b

• Revision f16cde998b : Tweaks to vpx_test android make file * Change from thumb mode to arm mode imp

  14 novembre 2013, par Joshua Litt

  Changed Paths :
   Modify /test/android/Android.mk

  
   Modify /test/android/README

  
  
  Tweaks to vpx_test android make file

  * Change from thumb mode to arm mode improves test time significantly
  * Direct inclusion of test.mk allows for unit test configuration via
  configure script
  Change-Id : Id58d3ba8289374528756a672459d8334afe20e2a

• Can I know which byte range to read from a remote mp4 file for FFMpeg to decode a keyframe ?

  12 octobre 2023, par db9117

  I need to decode a of keyframe of a video file (mp4, h264 encoded). I know the timestamp of the keyframe I want to extract/decode. I want to minimize amount of data being read in memory. For this, I need to know beforehand exactly the minimal byte range I would require that encompasses this keyframe. How do I know what is the minimal byte range in the whole mp4 byte stream I need to read in order to be able to decode the keyframe ?

  


  I currently find the appropriate keyframe in the index_entries contained in the header. I get its byte position (pos attribute) and timestamp (timestamp attribute). I calculate the range as follows :

  


  startBytes : minimum of :

  


  

  1. the pos of the keyframe

  


  2. the pos of the nearest index entry in the audio stream happening at or before the keyframe's timestamp.

  


  


  This way when it's decoding the frame, if it also needs the audio content for demuxing, it would have it.

  


  endBytes : maximum of :

  


  

  1. the pos of the next frame in the video stream's index, after the keyframe

  


  2. the pos of the next frame in the audio stream's index after the timestamp of the wished keyframe.

  


  


  This way I know that I have everything up until the next frame in the index, which theoretically should be enough to decode the keyframe only.

  


  I then read the appropriate byte range.

  


  When I try to decode the frame, I run in a loop until I succeed :

  


  

  • avcodec_read_frame

  


  • avcodec_send_packet

  


  • avcodec_receive_frame

  


  


  I ignore AVERROR(EAGAIN) errors.

  


  avcodec_receive_frame fails multiple times with error AVERROR(EAGAIN) which I ignore, until it fails saying that the memory it wants to read isn't available (wants to read after endBytes). I explicitly tell it to fail if it wants to read more than it has already read.

  


  Note : for other keyframes at other positions in other videos, it sometimes succeeds (probably because the range is big enough by chance), but it fails more often than not.

  


  My question is : Why is the end of the range not enough to be able to decode only the one keyframe ? Is there any way to more precisely calculate the exact range in bytes I would need in order to decode a particular keyframe ?